This invention relates to electrostatographic imaging systems and more particularly to an improved blade cleaning apparatus for cleaning electrostatographic image developer material from an imaging surface.
One method for cleaning of electrostatographic plates is disclosed in U.S. Pat. No. 3,552,850, to Royka et al. A flexible cleaning blade is used in pressure contact at the photoconductive surface to remove residual toner particles. Royka et al. also disclose that a dry solid lubricant may be supplied to the electrostatographic plate.
It is also known to supply slow translation to the cleaning blade in an electrostatographic plate cleaning apparatus. Such translation systems are described in detail in U.S. Pat. Nos. 3,724,019 to Shanley; 3,724,020 to Till; 3,740,789 to Ticknor; 3,847,480 to Fisher; and 3,854,814 to Jones. The systems described in the Shanley, Till, and Ticknor patents are similar in many respects to those employed commercially in the Xerox 3100 and 4000 copiers. In those systems the blade is slowly moved parallel to the drum axis in a reciprocal fashion. One of the features of those systems is that the slow sideways translation of the blade distributes the wear caused by an individual drum asperity over a relative large portion of the blade edge. This consequently extends blade life and reduces the occurrence of cleaning failures. It has also been found that slow translation of the blade for a few seconds after the drum had stopped is beneficial in breaking up particle accumulation developed between the blade and the photoconductive surface, thereby providing improved cleaning.
Copiers employing blade cleaning systems can be subject to random cleaning failures which can result in undesirable print-out on the copy sheet. For example, toner streaking which can print-out can be caused by a local tuck-under or folding under of the blade edge which contacts the photoconductive surface. Toner passing under the blade edge at the tuck-under forms the streak-type failure. Lubricants are employed in the commercial copiers to reduce the occurrence of such tuck-unders. Typical lubricants useful for this purpose are described in the Royka et al. patent.
In U.S. Pat. Nos. 3,848,992, to Smith, and 3,848,993 to Hasiotis, there are disclosed cleaning blade structures for cleaning dry toner from a photoreceptor surface without lubrication other than the toner itself. The blades comprise a sharpe-edged elastomer cleaning tip which is integrally mounted on a main blade portion of much more rigid and thin material such as steel shim stock. The shim stock extends out to closely adjacent the cleaning edge of the tip to fully support it. The blade structures described in these patents are effective to provide lubricantless blade cleaning of toner while substantially reducing the occurrence of tuck-under type cleaning failures.
In accordance with this invention a blade cleaning system is provided wherein the blade is vibrated at a high frequency to reduce the blade to imaging surface friction. The approach of the present invention should provide a still further improvement by reducing and perhaps eliminating tuck-under type failures.
In U.S. Pat. No. 3,617,123 to Emerson, a method and apparatus for cleaning residual toner material is provided wherein a brush mounted at the entrance to a development-cleaning station is vibrated to uniformly distribute residual toner over the entire area of the photoconductive surface to improve cleaning. The brush itself does not remove the toner.
In U.S. Pat. No. 3,483,034, to Ensminger, a method and apparatus for cleaning residual powder particles from the surface of the xerographic plate is provided in which the surface to be cleaned is submerged in a liquid medium and subjected to a source of sonic energy therein. Vibrations are induced into the liquid medium by the source of sonic energy to produce at the plate surface a turbulent scrubbing action to remove the powder particles.
In addition to the foregoing patents, numerous patents exist in fields outside electrostatography, which deal with the use of reciprocating, oscillatory, or vibrating doctor blades. Exemplary of oscillatory systems are U.S. Pat. Nos. 2,300,908; 2,544,557; 2,857,612; 2,972,767; and 3,130,439. Exemplary of vibrating systems are U.S. Pat. Nos. 2,885,069; 3,087,184; 3,389,655; and 3,617,123. U.S. Patent No. 3,087,184 in particular shows the use of a vibrating doctor blade mechanism to provide a self-cleaning action for the blade.
In blade cleaning of toner, the toner is not being doctored, rather the toner is preferably totally stopped by the cleaning blade or blades in a single rotation of the photoreceptor drum or surface, and simultaneously or subsequently removed from the surface. The entire surface must be cleaned thousands of times without damage. The cleaning loads on the blade are very uneven, both short term and long term, because the location, density and tenacity of the residual toner varies widely over the surface, depending on the images, the exposures, the surface charges, the toner development, the image border areas, etc. Furthermore, the frictional forces of the cleaning operation, unless carefully controlled, can easily result in the generation of excessive pressure or heat, resulting in physical and chemical changes in the toner, smearing to toner materials onto the photoreceptor, or blade, excessive photoreceptor wear, or other problems, especially in higher speed machines. Thus, cleaning dry toner from a photoreceptor presents extremely critical requirements not normally found in other cleaning fields and applications, e.g., cleaning or doctoring systems for metal gravure rollers or inking rollers or paper mill roller or adhesive applicators, are not normally appropriate.